A SQUID is known as a magnetic sensor that can detect a magnetic signal with the highest sensitivity, and has been used in measurement of a feeble biomagnetic signal generated from the brain, the heart or the like, non-destructive inspection using residual magnetism or eddy current detection, and recently in a very low magnetic field MRI (magnetic resonance imaging) or the like. However, a SQUID of a low-temperature superconductor that needs liquid helium for cooling which is expensive and hard to treat has been limited in the range of application of the SQUID. Since discovery of a high-temperature superconductor that exhibits superconducting characteristics at the temperature of liquid nitrogen, the development of a SQUID of a high-temperature superconductor that operates at the temperature of liquid nitrogen has been energetically advanced. A high-temperature superconducting magnetic sensor having a detection sensitivity of 100 fT/Hz1/2 or less is presently available for purchase, and a high-temperature superconducting magnetic sensor having a detection sensitivity of 10 fT/Hz1/2 or less has been reported in the leading edge of research and development. A high-temperature superconducting magnetic sensor (SQUID of a high-temperature superconductor) enables cooling using liquid nitrogen which is low in cost and easy to treat, and thus various structures have been proposed (see Non-Patent Literatures 1 to 8). The SQUID of a high-temperature superconductor enables the cooling using liquid nitrogen which is low in cost and easy to treat, and new applications such as non-destructive inspection have been proposed.